Process op treating rubber



UNITED STATES PATENT OFFICE.

JOSEPH PORZEL, OF BUFFALO, NEW YORK, ASSIGNOR, BY MESNE ASSIGNMENTS, TO SUPERIOR RUBBER COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

PROCESS OF TREATING RUBBER.

Specification of Letters Patent. Patented Apr, 12, 1921,

No Drawing. Application filed August '7, 1918, Serial No. 248,700. Renewed October 9, 1920. Serial To all whom it may concern:

Be it known that I, JOSEPH Forum, a citizen of the United States, residing at Buffalo, in the county of Erie and State of New York, have invented certain new and useful Improvements in Processes of Treating Rubber, of which the following is a specification.

This invention relates to a process of treating rubber. It is to be distinguished from so-called processes of reclaiming rubber, and also is to be distinguished from methods of mere admixture of old, vulcanized rubber with a suflicient amount of new rubber to produce an article wherein the new rubber mixed with the old rubber produces in some degree the characteristics of newly vulcanized rubber, due to the presence of a large percentage of new rubber.

The essence of my invention resides in the discovery that if vulcanized rubber, which is old or has lost its desirable qualities, is reduced practically to the limit of mechanical division, under conditions where the freshly exposed surfaces are kept from exposure to oxygen or other elements which deteriorate such surfaces, and if then or thereafter a very small amount of new, unvulcanized rubber, dissolved in a large amount of solvent, is carried over such freshly exposed surfaces, the solvent then removed, and the thus coated or filmed particles subjected to ordinary methods of formation and vulcanization, a substance will result which has very nearly the characteristics and values of the original rubber when first formed and vulcanized.

lVhile I do not assert positively as to what occurs, it is my belief that, while the grinding of the old rubber may, in some small measure, restore its activity, the valuable condition created is due to filming or coating the minute particles of old rubber with a very thin film of new rubber which, after vulcanization, gives to the product very nearly the qualities of the old rubber when the same was new and not deteriorated. Moreover, it is a condition other than that of a mere admixture of old rubber with new rubber wherein the beneficial qualities are due solely to the large amount of new rubber while the old rubber remains substan tially in an inert state, for the obvious reason that I employ so small a percentage of new rubber that it, acting alone and the old rubber acting merely as an inactive mass or filler, could not produce the conditions of resiliency, elasticity and other qualities of good rubber which I attain.

The object of my invention is, therefore, to restore to vulcanized rubber which has lost in a greater or less degree its valuable qualities, its original qualities as nearly as possible in a simple and effective manner; and I will now describe the simplest method of carrying out my invention.

The old rubber having been cleaned and freed from metallic and other foreign substances sufiiciently to permit of comminution, is then ground to a powder, practically to the limit of mechanical division, and under conditions where air and other deleterious gases are prevented from attacking the freshly exposed surfaces so far as is possible.

The next step is to mix such comminuted old rubber with a solution of new, unvulcanized rubber and a rubber solvent, which I shall hereafter term a solvent-cement. This solvent-cement consists of a very small amount of new rubber, as small as two pounds to one hundred pounds of comminuted, old rubber in some cases, and an exoess of rubber solvent sufficient in quantity to carry the new rubber over substantially all of the newly exposed surfaces, 6. 9. about a pint of solvent to an ounce of new rubber. I may use any well-known solvent, but name carbon tetrachlorid or gasolene as those especially desirable,the former being particularly so from the point of view of reduction of fire risk.

The mixing being completed by any wellknown means, the solvent is then driven off, leaving the particles of old rubber filmed with the new rubber. In this state the product is a comparatively dry powder, and is not readily attacked by the oxygen of air.

The next step is to form and vulcanize by well-known means. Under ordinary conditions the old, vulcanized rubber contains a sufiicient amount of free sulfur to effect the vulcanization of the very thin film of new rubber; but if the process is applied to desulfurized rubber or to rubber which contains an insulficient amount of sulfur, a suliicient amount of sulfur may be added with the solvent-cement. The amount of sulfur to be added under such circumstances will be determined readily by one skilled in the art.

The process may be varied somewhat; and I will new state two variations which may be employed. First, the old rubber may be ground to a condition somewhat less than its final comminution and ground dry as above indicated. Then the solvent-cement may be added and the mass reground. VVhen thus treated the solvent-cement will act as an air excluder to prevent oxidation. Second, the old rubber may be partially reduced as above stated with a part of the solvent-cement added, and then reground with the balance of the solvent-cement added. I have found this last method very efficient, apparently "for the reason that it acts to carry the new rubber over the surfaces of the old rubber thoroughly and uniformly. The remaining steps are the same in all cases mentioned.

It is distinctly to be understood that after grinding and mixing with the solventcement, the solvent must be driven on? nearly entirely as possible; for it it is permitted to remain in any material amount, its presence is evidenced by imperfections in the finished product.

In general'manufacture, using the ordinary run of scrap rubber, I have found that I attain the best results by using from twoand one-half to three pounds 01 ncw, unvulcanized rubber to one hundred pounds of old rubber, and an excess 01" solvent sufficient to insure thorough wetting of the mass. However, in some old or scrap rubber, the amount of actual rubber and filler may vary materially from the ordinary; and in such case, in carrying out my process, a person skilled in the art will take such variation into account and will use more or less new rubber as the case requires.

Having thus described my invention and the method of employinn,- the same, I claim:

1. The process of treating vulcanized rubher consisting of reducing the same to a finely divided state under conditions of e);- clusion of oxygen, adding, thereto a small quantity of new, unvulcanized rubber sufficient merely to film the particles of old rubber, which new rubber has been dissolved in an excess quantity of solvent sufiicient to dis tribute said new rubber over said particles,

driving" oil said solvent, and forming and vulcanizing in the usual manner.

2. The process oi treating vulcanized rubber which con ts of comminutiiug sai id rubber to c esh surfaces and protecting such sui from contact with oxygen 0] other deteriorating substance until the next step, filming said eomininuted rubber with new, uni-:ulcanized rubber by dissolving said new rubber in a solvent suliici nit in quantity to carry said new rubber over the freshly ex posed surfaces of the old rubber, whcrel'iy said solvent acts ooth as a solvent and a curricr and distributer of the new rubber, driving oll' said solvent, and 'li'orminn and vulcanizingin the usual manner.

The process oi? treating vulcauir-icd rubber which consists (l) in commiuutinn the same to uzuosc l resh surfaces and prcvculing ()Xli'lfil'lOll during and following said step; mixing with such old. comnuiuujcd rubber new, unvulcaiiizcd rubber dissolved in a solvent, the amount o't such new rubber being; sutiicient only to produce a very thin lihn over said freshly exposed slirluccri whilc the amount of said solvent is in sullicicut excess to act as a carrier of the new iubbcr to said fresh surfaces; (3) eliminating; said solvent; (a) forming and vulcauizinp; thc filmed old rubber.

T 1e process of treating vulcanized rubbcr consisting; oil (reomminuting the sainc and protecting the freshly exposed surfaces from deterioration in il they are lihnod, lihning said surfaces with new HDVlllCilllliiQd rubber in the proportions o' from two to live per cent. of new rubber to the old rubber, thc new rubber having been dissolved in an excess ol solvent to insure substantially coinplcte filming. driving oil the solvent, and forming; and vulcauizing in the usual manner.

The herein described process of tr atiu;r old rubber which consists in grinding: old rubber in the presence of a rubber solventcement diluted by excess solvent to carrv the new rubber to place about the surfaces of tho old rubber particles as they are cxposcd duvinn; grinding, and continuing such grinding; or 1iulverir-clug; process until the old i'ubbcihas been reduced appvoxiinatelv to the limit oi practical mechanical division. so that the solvent and new rubber ponelies to lhc limits of such mechanical division, driving off the solvent, and molding and vulcauizing.

JOSEPH POE ZEL. 

